JP-A-5-289450 discloses an existing image forming apparatus. The image forming apparatus includes a housing, a transport belt arranged in the housing and having a sheet transport face with which a back face of a sheet makes contact and configured to rotate to transport the sheet along the sheet transport face, an image forming portion of an electrophotographic type arranged on an upstream side of the sheet transport face of the transport belt in a sheet transport direction to face a front face side of the sheet in the housing for forming a toner image by transferring a toner on the front face of the sheet, and a fixing unit arranged on a downstream side of the sheet transport face in the sheet transport direction in the housing for fixing the toner image to the sheet.
The fixing unit includes a heating roller driven to rotate in contact with the front face of the sheet, and a pressure roller pressed to the heating roller from the back face side of the sheet for pressing the sheet along with the heating roller.
A partition wall for surrounding the image forming portion is arranged between the image forming portion and the heating roller. Further, the partition wall is provided with a single pair or a plurality of pairs of ribs projected to the sheet transport face. Each pair of ribs are configured to contact both sides of a sheet in a width direction in which the toner image is not formed so as to locate the sheet being transported away from the partition wall and guide it to the fixing unit.
According to the existing image forming apparatus structured above, after the toner image is formed on the front face of the sheet by the image forming portion, the sheet is transported to the fixing unit by the transport belt and the toner image is fixed to the sheet. At that occasion, the ribs guide the transported sheet so as not to make contact with the partition wall, and therefore, a failure in image quality brought about by rubbing the toner image on the front face of the sheet by the partition wall can be prevented.